JP4104150B2 - Polyester polyol production of polyhydric alcohol - Google Patents

Abstract

The invention provides a process for preparing polyester polyols of polyhydric alcohols by mono- or polyesterification of at least one carboxylic acid having at least two acid groups and/or at least one derivative of a dicarboxylic acid with polyhydric alcohols, optionally with the addition of a catalyst, while removing the water of reaction, wherein the polyhydric alcohol used has a formaldehyde acetal content of less than 500 ppm.

Description

  In the present invention, dicarboxylic acid and / or a derivative of dicarboxylic acid and a corresponding polyhydric alcohol are mono- or polyester-ized in a solvent and optionally by adding a catalyst while removing water of reaction. Relates to a method for producing a polyester polyol of a polyhydric alcohol.

  Polyhydric alcohols are compounds having two or more, generally 2 to 6, preferably 2 to 4, particularly preferably 2 or 3, hydroxyl groups.

  Such polyols are used as precursors for polyurethanes, polyesters and polyacrylates and are therefore used in harsh applications.

  These applications require special products (materials) with little, if any, color, essentially odorless and high storage stability.

  A method for producing a polyester polyol while removing water from a polyhydric alcohol and a dicarboxylic acid is generally known.

  The reaction is generally performed with a catalyst (eg, acid) or simply by increasing the temperature or by increasing the temperature under vacuum.

  Polyester polyols of polyhydric alcohols are generally unable to be purified by distillation because of their high boiling points, so that by-products remain in the target ester and are further processed and / or both the target ester and subsequent product. Affects the quality of the.

  The object of the present invention is to provide an economical method that enables the production of polyester polyols of polyhydric alcohols on an industrial scale, in a simple manner, without the addition of auxiliaries, with high purity and high yield. There is to do.

The above purpose is
A method for producing a polyester polyol by reacting a polyhydric alcohol with at least one dicarboxylic acid and / or a derivative of dicarboxylic acid (eg, acid anhydride), optionally in a solvent, while removing reaction water. There,
It has been found that the polyhydric alcohol is achieved by a production method characterized by using one having a formaldehyde acetal content of less than 500 ppm.

The new method has the following certain advantages:
The final product is hardly intensely colored, there is no change in the number of colors during different production methods, and the occurrence of haze or haze due to the components in the product can be avoided.

  Examples of the polyhydric alcohol used include trimethylolbutane, trimethylolpropane, trimethylolethane, neopentyl glycol, pentaerythritol, 2-ethyl-1,3-propanediol, and 2-methyl-1,3-propanediol. Glycerol, ditrimethylolpropane, dipentaerythritol, bisphenol A, bisphenol F, bisphenol B, bisphenol S, 2,2-bis (4-hydroxycyclohexyl) propane, 1,1-, 1,2-, 1,3- And 1,4-cyclohexanedimethanol, 1,2-, 1,3- or 1,4-cyclohexanediol, sorbitol, mannitol, diglycerol, erythritol or xylitol.

  In the method of the present invention, it is preferable to use these polyhydric alcohols obtained by reacting an aldehyde with formaldehyde and then converting the aldehyde group into a hydroxyl group.

  Examples of these include formula (I):

[Wherein R ¹ and R ² are each independently hydrogen, C ₁ -C ₁₀ -alkyl, C ₁ -C ₁₀ -hydroxyalkyl, carboxyl or C ₁ -C ₄ -alkoxycarbonyl, preferably hydrogen, alkyl, particularly preferably hydroxymethyl or C ₁ ~C ₁₀ - - hydroxymethyl or C ₁ -C ₁₀ alkyl. ]
The polyhydric alcohol represented by these can be mentioned.

  Each alkyl group may be linear or branched.

Examples of R ¹ and R ² are hydrogen, methyl, ethyl, iso-propyl, n-propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl , N-octyl, n-decyl, hydroxymethyl, carboxyl, methoxycarbonyl, ethoxycarbonyl or n-butoxycarbonyl, preferably hydrogen, hydroxymethyl, methyl and ethyl, particularly preferably hydroxymethyl, methyl and ethyl .

  Examples of polyhydric alcohols of formula (I) include trimethylolbutane, trimethylolpropane, trimethylolethane, neopentyl glycol, pentaerythritol, 2-ethyl-1,3-propanediol, 2-methyl-1,3 -Propanediol, 1,3-propanediol, dimethylolpropionic acid, dimethylolpropionate methyl, dimethylolpropionate ethyl, dimethylolbutyrate, dimethylolbutyrate or dimethylolbutyrate, preferably neopentylglycol, Trimethylolpropane, pentaerythritol and dimethylolpropionic acid, particularly preferably trimethylolpropane and pentaerythritol, especially trimethylolpropane.

  Such polyhydric alcohols of formula (I) are, for example, those of formula (II):

[However, R ¹ and R ² are as defined above. ]
Is obtained by reacting aldehyde represented by formula with formaldehyde, and then converting the aldehyde group to a hydroxyl group.

  In order to produce the polyester polyol of the present invention, a carboxylic acid having at least two acid groups can be used as the acid, preferably an aliphatic or aromatic dicarboxylic acid, particularly one having 2 to 12 carbon atoms. Is preferred. Examples of useful dicarboxylic acids include adipic acid, succinic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, dimeric and / or trimeric fatty acids, Preferred are adipic acid, phthalic acid, isophthalic acid, terephthalic acid and isomeric naphthalenedicarboxylic acid. The dicarboxylic acids can be used individually or as a mixture. Instead of dicarboxylic acids, the corresponding dicarboxylic acid derivatives such as dicarboxylic acid esters with alcohols having 1 to 4 carbon atoms, or dicarboxylic acid anhydrides can also be used. Dicarboxylic acid mixtures of succinic acid, glutaric acid and adipic acid (e.g. mixtures of 20 to 35:35 to 50:20 to 32 parts by weight), in particular phthalic acid and / or a mixture of phthalic anhydride and adipic acid, phthalic A mixture of acid / anhydride, isophthalic acid and adipic acid, or a dicarboxylic acid mixture of succinic acid, glutaric acid and adipic acid, and a mixture of terephthalic acid and adipic acid, or a dicarboxylic acid mixture of succinic acid, glutaric acid and adipic acid. preferable. For use in rigid polyurethane foams, it is preferred to use aromatic carboxylic acids or mixtures containing aromatic carboxylic acids. At the same time, it is preferred to use fatty acids and their derivatives and dimeric and / or trimeric fatty acids individually or in mixtures. Polyester alcohols based on long chain carboxylic acids (especially fatty acids) can be preferably used to produce alkyd resins that can be further processed into coatings.

  The alcohol of the general formula (I) can be used in a mixture with another polyhydric alcohol, preferably a diol (having 2 to 12 carbon atoms, in particular having 2 to 6 carbon atoms). Examples of di- or polyhydric alcohols, in particular diols, include ethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1, Mention may be made of 6-hexanediol, 1,10-decanediol, glycerol and trimethylolpropane. Ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol, or a mixture of two or more of these diols are preferred, especially 1,4-butanediol, 1,5 A mixture of pentanediol and 1,6-hexanediol is preferred. It is also possible to use polyester polyols of lactones (eg ε-caprolactone), hydroxycarboxylic acids (eg ω-hydroxycaproic acid and hydroxybenzoic acid).

  If desired, monofunctional alcohols and / or carboxylic acids can be used in multifunctional alcohols and mixtures of multifunctional alcohols and carboxylic acids to adjust functionality. Examples of monofunctional carboxylic acids include monomeric fatty acids such as oleic acid or ricinoleic acid. Examples of monomeric alcohols include aliphatic alcohols having 1 to 15 (preferably 2 to 10) carbon atoms, such as hexanol, octanol, nonanol or decanol.

  Especially with respect to the polyester alcohol, but at a maximum amount of 50% by weight, if it has a functionality of more than 2, unnecessary crosslinking occurs and is accompanied by an increase in the viscosity of the polyester polyol. It is preferable to use it.

  In order to produce polyester polyols, organic, for example aliphatic and preferably aromatic carboxylic acids, and mixtures of aromatic and aliphatic polycarboxylic acids and / or derivatives with polyhydric alcohols are used as catalyst. The polycondensation can be carried out in the absence or preferably in the presence of an esterification catalyst. The polycondensation is advantageously performed under reduced pressure, optionally in a molten state at a temperature of 150 to 250 ° C., preferably 180 to 220 ° C., in an atmosphere of an inert gas (eg nitrogen, carbon monoxide, helium, argon, etc.). Under the desired acid number (less than 10 is advantageous, preferably less than 2). In order to produce a polyester polyol, an organic polycarboxylic acid and / or derivative and a polyhydric alcohol can be polycondensed in a molar ratio of 1: 1 to 1.8, preferably 1: 1.05 to 1.2. It is advantageous.

  The catalyst used is an acidic catalyst such as toluenesulfonic acid, preferably an organometallic compound, in particular a specific compound based on titanium or tin (eg titanium tetrabutoxide or tin (II) octoate).

  It is also possible to first react a polyhydric alcohol with an alkylene oxide to obtain a polyether alcohol, which is then esterified with a carboxylic acid. It is likewise possible to add an alkoxylation catalyst to the polyester alcohol produced according to the process of the invention and to which an alkylene oxide is added. The polyetheresterol thus obtained is noted for its good compatibility with polyetherol and polyesterol, and can also be used for the production of polyurethane.

  Polyhydric alcohol (I) is obtained on an industrial scale by condensing formaldehyde with higher CH-acidic aldehyde (II) or with water and acrolein or 2-alkylacrolein. This reaction is distinguished between two basic variants for carrying out the conversion of aldehyde groups to hydroxyl groups, which are shown below by the production of trimethylolpropane. However, it is not limited to these.

First, there are cannizzaro methods classified into inorganic and organic cannizzaro methods. In an inorganic variant, excess formaldehyde is combined with a suitable aldehyde (II) (eg, n-butyraldehyde) in the presence of a stoichiometric amount of an inorganic base (eg, NaOH or Ca (OH) ₂ ). react. The dimethylol butanal formed in the first stage reacts with an excess of formaldehyde in a disproportionation reaction in the second stage to give trimethylolpropane and the base formate used (eg sodium formate or calcium formate). The generation of this salt is disadvantageous because it is difficult to remove the salt thus generated from the reaction product and furthermore, an equal amount of formaldehyde is lost.

  In the Cannizzaro process, tertiary alkyl amines are used instead of inorganic bases. This achieves a higher yield than when an inorganic base is used. A trialkylammonium formate salt is obtained, which is an unwanted by-product. One equivalent of formaldehyde is therefore lost as well.

  The disadvantages of the Cannizzaro method are avoided by the hydrogenation method. This process involves reacting formaldehyde with the appropriate aldehyde (II) in the presence of a catalytic amount of amine. This makes it possible to substantially stop the reaction at the alkylolated aldehyde stage. After removal of formaldehyde, the reaction mixture containing a small amount of a suitable polyhydric alcohol and a small amount of acetal of the alcohol formed, as well as the alkylolated aldehyde, is subjected to catalytic hydrogenation to give the desired polyhydric alcohol.

  A particularly effective method for producing polyhydric alcohols obtained by condensation of aldehydes with formaldehyde is described in WO 98/28253. This method makes it easy to increase the yield while generating very little coupling product. The procedure involves reacting the higher aldehyde in the presence of 2-8 times the amount of formaldehyde with a tertiary amine and separating the reaction mixture thus obtained into two solutions, one of which is completely methylol. And the other contains unconverted starting products (materials). The latter solution is recycled to the reaction system. Separation takes place by distillation or by simple removal of the aqueous phase from the organic phase. The solution containing the product is subjected to catalytic treatment and / or heat treatment in order to convert the incompletely alkylolated alkanal into the desired fully methylolated compound. All by-products produced are removed by distillation and the liquid phase thus obtained undergoes catalytic hydrogenation leading to polyhydric alcohols.

  In the process according to the invention for the production of polyester polyols, the formula obtained by the hydrogenation process, i.e. by reacting the aldehyde of formula (II) with formaldehyde and then converting the aldehyde groups to hydroxyl groups by catalytic hydrogenation. It is preferable to use the polyhydric alcohol (I). In particular, polyhydric alcohols obtained by the method described in WO 98/28253 are preferred.

  It is the essence of the invention that the formaldehyde acetal in the polyhydric alcohol used is less than 500 ppm by weight and preferably less than 400 ppm.

  Formaldehyde acetal (formal) has the following structural units:

を含む環式又は脂肪族化合物である。

Is a cyclic or aliphatic compound containing

  These may be either hemiacetals or complete acetals, such acetals are derived from the main components and impurities, or else by-products, intermediates or secondary formation of the reaction mixture It is derived from things.

  These can be, for example, formaldehyde acetals represented by the following formula (IV):

In the above formula, R ¹ and R ² are as defined above, and R ³ is linear or branched C ₁ -C ₁₀ -alkyl (preferably C ₁ -C ₈ -alkyl, more preferably C ₁ -C ₅ - alkyl), linear or branched C ₁ -C ₁₀ - hydroxyalkyl (preferably C ₁ -C ₈ - hydroxyalkyl, more preferably C ₁ -C ₆ - hydroxyalkyl), or hydrogen,
n is an integer of 1 to 4 (preferably an integer of 1 to 3, more preferably 1 or 2).

Examples of R ³ are hydrogen, methyl, ethyl, n-propyl, n-butyl, 2-methylpropyl, 2-methylbutyl, 2-ethyl-3-hydroxypropyl, 2-methyl-3-hydroxypropyl, 2, 2-bis (hydroxymethyl) butyl, 2,2-bis (hydroxymethyl) propyl, 2,2-dimethyl-3-hydroxypropyl, 3-hydroxypropyl, 3-hydroxy-2- (hydroxymethyl) propyl or 3- Mention may be made of hydroxy-2,2-bis (hydroxymethyl) propyl.

  Preferred formaldehyde acetals are:

In the above formula, R ¹ and R ² are as defined above.

  More preferably, the formaldehyde acetal is IVa, IVb (n = 1), IVb (n = 2) and IVc.

  Methanol acetal is formed from methanol, which is generally present at a low concentration in formaldehyde or is formed in small amounts during the production of formaldehyde by the Cannizzaro reaction.

In the synthesis of the trihydric alcohol trimethylolpropane (TMP) from formaldehyde and n-butyraldehyde in the presence of a catalytic amount of trialkylamine, for example, typical formaldehyde acetals are IVa, IVb (n = 1), IVb. (N = 2) and IVc (R ¹ is ethyl and R ² is hydroxymethyl), each of which is present in the crude product of the hydrogenation process at 0.05 to 10% by weight. May be.

  The formaldehyde acetal content is calculated from the sum of the molar mass proportions of formaldehyde equivalents in each formaldehyde acetal multiplied by the analytically measured mass fraction in the reaction mixture.

For example, the formaldehyde acetal content of a trimethylolpropane mixture (R ¹ = ethyl, R ² = hydroxymethyl) containing components (IVa), (IVb (n = 1, n = 2)) and (IVc) is as follows: Calculated to:
Formaldehyde acetal content [% by mass] =
(Mass% of (IVa)) × (30 g / mol) / (146 g / mol) +
(Mass% of (IVb (n = 1))) × (30 g / mol) / (178 g / mol) +
(Mass% of (IVb (n = 2))) × (2 × 30 g / mol) / (208 g / mol) +
(Mass% of (IVc)) × (30 g / mol) / (280 g / mol)

  This value must be multiplied by 10,000 in order to obtain the corresponding formaldehyde acetal content (in ppm by mass).

  The content of each component can be measured by a skilled technician by an analysis method known per se (eg, gas chromatography or HPLC). For example, each component can be identified by combining the analysis method described above with mass spectrometry.

  It is irrelevant to the present invention how to obtain such a low formaldehyde acetal content in the polyhydric alcohol.

  US 6096905 discloses a method in which a composition containing formaldehyde acetal is treated with a strong acid catalyst at 30 to 300 ° C. for 1/2 to 8 hours.

  GB-A1290036 discloses a method of treating a crude TMP solution obtained by an inorganic cannizzaro method with a cation exchanger.

  A preferred method by which the formaldehyde acetal content of the polyhydric alcohol can be reduced is that the polyhydric alcohol is purified by distillation after production, then heat treated, and then purified again (preferably distilled). This method is described in the German application (reference date: June 13, 2000, BASF Aktiengesellschaft) with the reference number 10029055.8 or in the international application (BASF) with the name “Removal of formaldehyde acetal from polyhydric alcohols by heat treatment”. Actchen Gesell shaft).

  When polyhydric alcohols are used in such a heat treatment step, particularly good results are obtained in which the content exceeds 60%, preferably more than 75%, more preferably more than 90%, particularly preferably more than 95%, especially 98%. It can be obtained when excess alcohol solution is used. Examples of other components of the alcohol solution can include solvents, such as water, methanol, ethanol or n-butanol, and by-products generated during the production of polyhydric alcohols, which are preferably less than 10% by weight. More preferably, it is contained in the solution in an amount of less than 5% by mass, most preferably less than 2% by mass.

  This method can be used to reduce the formaldehyde acetal content in polyhydric alcohols (preferably alcohols of the formula (I), particularly preferably trimethylolpropane of any origin). The input may be an organic or inorganic cannizzaro process. The best results were obtained when the alcohol produced by the hydrogenation process was used in a way that functions to reduce formaldehyde acetal. In any case, it is important that the alcohol is pre-purified and has a purity in the aforementioned range.

  When the above method is used to remove formaldehyde acetal from a crude solution of a polyhydric alcohol (particularly trimethylolpropane having a product content of 60-95% by weight), the crude obtained after the hydrogenation process (step). The product (hydrogenated effluent) is preferably dehydrated before the heat treatment step. In the dehydration process, water and other low boilers (eg, methanol and trialkylamine or trialkylammonium formate salt) are removed by distillation.

  In this way, certain reaction conditions must be maintained to achieve the desired reduction in formaldehyde acetal content. The reaction conditions can vary depending on, for example, the type of polyhydric alcohol used, the purity of the product used, the equipment used and other components or additives. The reaction conditions can be obtained from experiments by the skilled technician.

  In general, the heat treatment step is carried out at a temperature of 100 to 300 ° C., preferably 160 to 240 ° C., for 5 minutes to 24 hours, preferably 15 minutes to 4 hours, 100 mbar to 200 bar, preferably 1 to 10 bar. Performed at pressure.

  When the polyhydric alcohol to be purified is trimethylolpropane, the heat treatment step is performed at a temperature of 100 to 300 ° C, preferably 160 to 240 ° C, 10 minutes to 24 hours, preferably 30 minutes to 6 hours, more preferably. It is carried out at a residence time of 45 minutes to 4 hours and above pressure.

  To carry out the heat treatment step, conventional equipment known to the skilled technician can be used continuously or in batches. In the batch operation, it is preferable to perform the heat treatment in a stirring vessel, and in the batch procedure of the tubular reactor, it is preferable to use either the liquid phase or the trickle method.

  The most preferred embodiment of the heat treatment is continuous operation in a tubular reactor in the liquid phase method.

In all of these operational variations, to achieve a better mixing of the components, the reaction vessel is a conventional dense packing known to those skilled in the art, such as a Raschig ring or a pole ring, or a structure. Packing, for example, plate-like metal packing is provided. In order to accelerate the progress of the reaction in the heat treatment step, the support and / or catalyst can also be present in conventional form, for example in the form of extrudates or tablets. Examples of suitable carriers / _{catalysts, TiO 2, Al 2 O 3} , SiO 2, can be mentioned supported phosphoric acid (H ₃ PO ₄₎ and zeolite.

In one variation of the heat treatment step, suitable additives are added to the reaction solution during the heat treatment step to accelerate and facilitate the reaction that results in a reduction in the amount of formaldehyde acetal. Examples thereof include less strong acids and / or reducing acids or their anhydrides or ion exchangers, which are described in US Pat. No. 6,096,905 or GB1290036. Examples of suitable acids include phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid, carbonic acid and sulfurous acid. Also suitable are gases that react with acid catalysts in aqueous solutions, such as CO ₂ and SO ₂ .

  The acid used as an additive is used in an amount of 10 ppm to 1% by mass, preferably 100 to 2000 ppm. Since the additive that can be added must be removed from the polyhydric alcohol with reduced formaldehyde acetal after the heat treatment step, this additive is preferably a gas, thereby removing it from the reaction mixture by outgassing. Is easy.

  Furthermore, it may be advantageous to perform a heat treatment step to decompose the formaldehyde acetal in the presence of an inert gas (eg, nitrogen, argon or helium, preferably nitrogen).

  While not wishing to be bound by theory, formaldehyde acetal is converted to high boiling non-volatiles and low boiling components by heat treatment in alcohol pre-purified by distillation and then more easily removed by distillation. It is speculated that it can be done.

  Polyhydric alcohols having a low formaldehyde acetal content can be easily removed from the high boiling non-volatile components formed by distillation. For this reason, distillation is performed after a heat treatment process. Since the non-volatile components formed from formaldehyde acetal in the heat treatment step differ significantly from polyhydric alcohols in terms of boiling point behavior, they can be removed by simple distillation means or methods having only a small separation action. A separation device having only one distillation step, for example a falling film evaporator, or a thin layer evaporator, is often sufficient. In particular, if the distillation is also responsible for further purification of the product alcohol, more complex separation methods or equipment can optionally be used, generally columns having more than one separation stage (distillation tower), eg irregular A packed column, bubble tray column or column with structural packing can optionally be used.

  It will be appreciated that distillation can be carried out using conventional conditions relating to pressure and temperature known to those skilled in the art, but these depend on the alcohol of the product (material) used.

  According to another aspect, the heat treatment may be combined with distillation. In this embodiment, the heat treatment is performed at the bottom of the distillation apparatus that removes the product polyhydric alcohol from the nonvolatile components and other impurities formed by the heat treatment. When the heat treatment step and distillation are combined in a single stage, it is important to maintain the aforementioned conditions regarding pressure, temperature and especially residence time so that sufficient decomposition of formaldehyde acetal is obtained. When combining the heat treatment step and the distillation step in a single step, it is preferable to add an acid.

  The polyhydric alcohol obtained by this method generally has a formaldehyde acetal content of less than 500 ppm, preferably less than 400 ppm, as defined above.

  It does not matter which method the polyhydric alcohol is obtained by, for example, the Cannizzaro method or the hydrogenation method.

  The polyester polyol produced by the method of the present invention can be reacted with, for example, polyisocyanate to form a polyurethane.

  Unless otherwise noted, the ppm and% data used in this document refer to ppm and% by mass.

  The APHA color number was measured according to DIN-ISO 6271.

[Method for producing polyester polyol for industrial rigid foam]
[Example I]
A laboratory stirrer equipped with a heating section, nitrogen bubbler, random packed column and distillation apparatus was charged with 204.1 g oleic acid, 105.6 g adipic acid, 214.1 g phthalic anhydride and 541.2 g TMP (formaldehyde). Acetal content 280 ppm, diformalin and methanol content 0.4%) was first charged and heated to 170 ° C. with stirring. After removing 60.4 g of water from the reaction system, the temperature was raised to 220 ° C. While continuing to remove the distillate that formed, the reaction was carried out until the acid number was less than 0.5 mg KOH / g.

[Examples II and III] (Comparison)
According to Example I, the synthesis was repeated using TMP with a formaldehyde acetal content of 620 ppm and 1400 ppm.

Claims (6)

At least one carboxylic acid having at least two acid groups and / or a derivative of at least one dicarboxylic acid and trimethylolpropane, neopentylglycol or pentaerythritol , optionally adding a catalyst, A process for producing a polyester polyol of trimethylolpropane, neopentyl glycol or pentaerythritol by mono- or polyesterification while removing,
A production method using a trimethylolpropane, neopentyl glycol or pentaerythritol having a formaldehyde acetal content of less than 500 ppm and more than 0 ppm . The production method according to claim 1 , wherein trimethylolpropane, neopentyl glycol or pentaerythritol is purified by distillation after production, then heat-treated, and then purified again. The method according to claim 2 , wherein the heat treatment is performed at 100 to 300 ° C. The production method according to claim 1, wherein the carboxylic acid having at least two acid groups is an aliphatic or aromatic dicarboxylic acid having 2 to 12 carbon atoms. The process according to claim 1, wherein the monofunctional carboxylic acid is used in a mixture with a carboxylic acid having at least two acid groups. For the esterification of at least one polyfunctional carboxylic acid, less than 500 ppm, and trimethylol propane with formaldehyde acetal content of 0ppm excess, trimethylol propane to use neopentyl glycol or pentaerythritol, neopentyl glycol Or the manufacturing method of the polyester polyol of a pentaerythritol .